1. Field of the Invention
The present invention relates to a cooling control unit for a water-cooled multi-cylinder internal combustion engine having a cylinder deactivation mechanism.
2. Description of Background Art
In a multi-cylinder internal combustion engine of a type capable of deactivating some of its cylinders, the cylinders which have been deactivated for a long time are sometimes incompletely warmed up when the engine returns to an operating condition with all of the cylinders being activated.
For the purpose of preventing such an incomplete warm-up condition, a certain multi-cylinder internal combustion engine is controlled in such a manner that the engine valves can repeatedly alternate their own activation and deactivation according to a previously set engine valve operation and stoppage modes while the engine is operated with some cylinders being deactivated. See, for example, Japanese Patent Application No. Hei. 8-93516.
In the case of the multi-cylinder internal combustion engine having a cylinder deactivation mechanism disclosed in Japanese Patent Application No. Hei. 8-93516, each of its cylinders is provided with valve activation/deactivation switching means for switching its corresponding engine valves between their activation and deactivation independently of the rest of the cylinders.
In this case, the multiple cylinders are provided with their respective valve activation/deactivation switching means. This increases the number of component parts, and makes the control of the cylinders complicated. In addition, the arrangement of the valve activation/deactivation switching means makes the structure of the internal combustion engine complicated, and increases the manufacturing costs.